The invention concerns electroluminescent diode components suitable in particular for surface-mounting on a printed circuit board, in which a housing base body produced by injection molding and comprising partially embedded electrical connector strips is provided with a recess, preferably implemented as a reflector, that has a radiation window aimed at the front side of the component housing. The recess, in which an electromagnetic-radiation-emitting chip is disposed, is filled for example with an encapsulant that is transparent to the electromagnetic radiation emitted by the chip.
Such component housings are also suitable for use with radiation-detecting chips, in which case the radiation window must be transparent to electromagnetic radiation that is to be received by the chip.
The present patent application claims the priority of German Patent Application 10243247.3, whose disclosure content is hereby incorporated by reference.
The invention is suitable in particular for use with radiation-emitting components in which the chip is installed in a so-called premolded leadframe. This means that each leadframe is overmolded with a housing base body before the chip is mounted.
In the production of such a component housing, the connector strips are first partially stamped into a leadframe ribbon. The leadframe ribbon is then placed in a two-part injection mold which forms a cavity around the leadframe that serves to create the housing base body.
An injection compound, e.g. a white plastic, is then fed in through an injection nozzle, for example via the portion of the injection mold adjoining the back side of the leadframe, i.e. into the portion of the cavity adjoining the back side of the leadframe, and fills the entire cavity of the injection mold.
After the injection compound has at least partially solidified, the injection mold is opened. As the leadframe is removed from the mold, the injection compound located in the injection nozzle is torn away from the injection compound located in the cavity. In addition, the chip is preferably arranged on one of the connector strips in the recess provided for it, connected in an electrically conductive manner to the connector strips and provided with encapsulant. After this, the components interconnected by the leadframe ribbon can be separated from one another and thereby singulated from this interconnected structure.
A radiation-emitting component of the aforesaid kind is described, for example, in EP 0 400 176 A1. The component comprises a housing base body with a mounting area in which a leadframe is partially embedded. Portions of the leadframe are formed as connector strips that project from the housing base body and, as they proceed further, are bent so that their connection areas lie in one plane with the mounting area, which defines the mounting plane of the component.
The overall height of components produced in this manner can be reduced to less than about 1 mm only with high technical outlay, if at all. The minimum height of the front portion of the housing base body is then about
0.5 mm, that of the back wall of the housing base body about 0.3 mm, and the thickness of the connector strips about 0.1 mm.
The reason for this is that the layer thickness of the injection compound located in the cavity between the leadframe and the tear-off site at the injection nozzle must be great enough to prevent delamination between the back side of the leadframe and the injection compound, insofar as possible. Such delamination would drastically increase the risk of damage to the component during further processing or later on during operation. Current knowledge has it that the above-cited layer thickness of the injection compound must be so great that the mechanical tensile forces occurring in the injection compound during tear-off from the injection nozzle can be reduced to a level such that the forces exerted at the boundary with the leadframe are not sufficient to tear the injection compound away from the leadframe.
However, to permit, for example, a very small overall height on printed circuit boards and/or complete countersinking particularly into round openings (bores) in printed circuit boards, the height of the components must be kept as small as possible, and there is a pressing need to reduce the overall height far below the above-cited critical height of about 1 mm. In some applications, especially in mobile communication terminals, the radiation-emitting components should have a much smaller height.
The possibility of reducing the overall height of components by decreasing the height of the housing base body on the chip side is severely limited owing to the final height of the radiation-emitting chip. The possibility of reaching the stated goal by simply reducing the thickness of the housing base body on the back side of the leadframe is also severely limited, since, as explained above, if the layer of injection compound used to form the back side of the housing is too thin, it will easily be torn away with the injection nozzle that is to be removed during the injection process used to produce the housing, in which case the hermeticity and thus the operation of the component can be disrupted.